1. Field of the Invention
The present invention relates to wireless communication systems, and more particularly, to a method and apparatus for entering an authentication key which is used to authenticate mobile stations in a cellular radio system.
2. History of the Prior Art
Cellular mobile telephony is one of the fastest growing segments in the worldwide telecommunications market. Between 1984 and 1992, for example, the number of mobile telephone subscribers in the United States grew from around 25,000 to over 10 million. It is estimated that the number of subscribers will rise to nearly 22 million by year end 1995 and to 90 million by the year 2000.
Cellular telephone service operates much like the fixed, wireline telephone service in homes and offices, except that radio frequencies rather than telephone wires are used to connect telephone calls to and from the mobile subscribers. Each mobile subscriber is assigned a private (10 digit) directory telephone number and is billed based on the amount of "airtime" he or she spends talking on the cellular telephone each month. Many of the service features available to landline telephone users, e.g., call waiting, call forwarding, three-way calling, etc., are also generally available to mobile subscribers.
In the United States, cellular licenses are awarded by the Federal Communications Commission (FCC) pursuant to a licensing scheme which divides the country into geographic service markets defined according to the 1980 Census. Only two cellular licenses are awarded for each market. The two cellular systems in each market are commonly referred to as the "A" system and "B" system, respectively. Each of the two systems is allocated a different frequency block in the 800 MHz band (called the A-band and B-band, respectively). To date, the FCC has released a total of 50 Mhz for cellular services (25 MHz per system).
Mobile subscribers have the freedom to subscribe to service from either the A-system or the B-system operator (or both). The local system from which service is subscribed is called the "home" system. When travelling ("roaming") outside the home system, a mobile subscriber may be able to obtain service in a distant system if there is a roaming agreement between the operators of the home and "visited" systems.